Reorganization of Synaptic Connections and Perineuronal Nets in the Deep Cerebellar Nuclei of Purkinje Cell Degeneration Mutant Mice.

The perineuronal net (PN) is a subtype of extracellular matrix appearing as a net-like structure around distinct neurons throughout the whole CNS. PNs surround the soma, proximal dendrites, and the axonal initial segment embedding synaptic terminals on the neuronal surface. Different functions of the PNs are suggested which include support of synaptic stabilization, inhibition of axonal sprouting, and control of neuronal plasticity. A number of studies provide evidence that removing PNs or PN-components results in renewed neurite growth and synaptogenesis. In a mouse model for Purkinje cell degeneration, we examined the effect of deafferentation on synaptic remodeling and modulation of PNs in the deep cerebellar nuclei. We found reduced GABAergic, enhanced glutamatergic innervations at PN-associated neurons, and altered expression of the PN-components brevican and hapln4. These data refer to a direct interaction between ECM and synapses. The altered brevican expression induced by activated astrocytes could be required for an adequate regeneration by promoting neurite growth and synaptogenesis.

The development and activity-dependent expression of aggrecan in the cat visual cortex.

The Cat-301 monoclonal antibody identifies aggrecan, a chondroitin sulfate proteoglycan in the cat visual cortex and dorsal lateral geniculate nucleus (dLGN). During development, aggrecan expression increases in the dLGN with a time course that matches the decline in plasticity. Moreover, examination of tissue from selectively visually deprived cats shows that expression is activity dependent, suggesting a role for aggrecan in the termination of the sensitive period. Here, we demonstrate for the first time that the onset of aggrecan expression in area 17 also correlates with the decline in experience-dependent plasticity in visual cortex and that this expression is experience dependent. Dark rearing until 15 weeks of age dramatically reduced the density of aggrecan-positive neurons in the extragranular layers, but not in layer IV. This effect was reversible as dark-reared animals that were subsequently exposed to light showed normal numbers of Cat-301-positive cells. The reduction in aggrecan following certain early deprivation regimens is the first biochemical correlate of the functional changes to the γ-aminobutyric acidergic system that have been reported following early deprivation in cats.

Perisynaptic aggrecan-based extracellular matrix coats in the human lateral geniculate body devoid of perineuronal nets.

The extracellular matrix surrounds different neuronal compartments in the mature nervous system. In a variety of vertebrates, most brain regions are loaded with a distinct type of extracellular matrix around the somatodendritic part of neurons, termed perineuronal nets. The present study reports that chondrotin sulfate proteoglycan-based matrix is structured differently in the human lateral geniculate body. Using various chondrotin sulfate proteoglycan-based extracellular matrix antibodies, we show that perisomatic matrix labeling is rather weak or absent, whereas dendrites are contacted by axonal coats appearing as small, oval structures. Confocal laser scanning microscopy and electron microscopy demonstrated that these typical structures are associated with synaptic loci on dendrites. Using multiple labelings, we show that different chondrotin sulfate proteoglycan components of the extracellular matrix do not associate exclusively with neuronal structures but possibly associate with glial structures as well. Finally, we confirm and extend previous findings in primates that intensity differences of various extracellular matrix markers between magno- and parvocellular layers reflect functional segregation between these layers in the human lateral geniculate body.

Inhibition of neuronal nitric oxide synthase prevents MPTP-induced parkinsonism in baboons.

1-Methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) produces clinical, biochemical and neuropathologic changes reminiscent of those which occur in idiopathic Parkinson's disease. 7-Nitroindazole (7-NI) is a relatively selective inhibitor of the neuronal isoform of nitric oxide synthase (NOS) that blocks MPTP neurotoxicity in mice. We now show that 7-NI protects against profound striatal dopamine depletions and loss of tyrosine hydroxylase-positive neurons in the substantia nigra in MPTP-treated baboons. Furthermore, 7-NI protected against MPTP-induced motor and frontal-type cognitive deficits. These results strongly implicate a role of nitric oxide in MPTP neurotoxicity and suggest that inhibitors of neuronal NOS might be useful in treating Parkinson's disease.

Neuroprotective effects of creatine in a transgenic animal model of amyotrophic lateral sclerosis.

Mitochondria are particularly vulnerable to oxidative stress, and mitochondrial swelling and vacuolization are among the earliest pathologic features found in two strains of transgenic amyotrophic lateral sclerosis (ALS) mice with SOD1 mutations. Mice with the G93A human SOD1 mutation have altered electron transport enzymes, and expression of the mutant enzyme in vitro results in a loss of mitochondrial membrane potential and elevated cytosolic calcium concentration. Mitochondrial dysfunction may lead to ATP depletion, which may contribute to cell death. If this is true, then buffering intracellular energy levels could exert neuroprotective effects. Creatine kinase and its substrates creatine and phosphocreatine constitute an intricate cellular energy buffering and transport system connecting sites of energy production (mitochondria) with sites of energy consumption, and creatine administration stabilizes the mitochondrial creatine kinase and inhibits opening of the mitochondrial transition pore. We found that oral administration of creatine produced a dose-dependent improvement in motor performance and extended survival in G93A transgenic mice, and it protected mice from loss of both motor neurons and substantia nigra neurons at 120 days of age. Creatine administration protected G93A transgenic mice from increases in biochemical indices of oxidative damage. Therefore, creatine administration may be a new therapeutic strategy for ALS.

Monoclonal antibody Cat-315 detects a glycoform of receptor protein tyrosine phosphatase beta/phosphacan early in CNS development that localizes to extrasynaptic sites prior to synapse formation.

Perineuronal nets (PNs) are lattice-like condensations of the extracellular matrix (ECM) that envelop synapses and decorate the surface of subsets of neurons in the CNS. Previous work has suggested that, despite the fact that PNs themselves are not visualized until later in development, some PN component molecules are expressed in the rodent CNS even before synaptogenesis. In the adult mammalian brain, monoclonal antibody Cat-315 recognizes a glycoform of aggrecan, a major component of PNs. In primary cortical cultures, a Cat-315-reactive chondroitin sulfate proteoglycan (CSPG) is also expressed on neuronal surfaces and is secreted into culture media as early as 24 h after plating. In this study, we show that in primary cortical cultures, the Cat-315 CSPG detected in early neural development is expressed in extrasynaptic sites prior to synapse formation. This suggests that ECM components in the CNS, as in the neuromuscular junction (NMJ), may prepattern neuronal surfaces prior to innervation. We further show that while the Cat-315-reactive carbohydrate decorates aggrecan in the adult, it decorates a different CSPG in the developing CNS. Using receptor protein tyrosine phosphatase beta (RPTPbeta/protein tyrosine phosphatase zeta) knock-out mice and immunoprecipitation techniques, we demonstrate here that in the developing rodent brain Cat-315 recognizes RPTPbeta isoforms. Our further examination of the Cat-315 epitope suggests that it is an O-mannose linked epitope in the HNK-1 family. The presence of the Cat-315 reactive carbohydrate on different PN components--RPTPbeta and aggrecan--at different stages of synapse development suggests a potential role for this neuron-specific carbohydrate motif in synaptogenesis.

Extended therapeutic window for caspase inhibition and synergy with MK-801 in the treatment of cerebral histotoxic hypoxia.

In rats, striatal histotoxic hypoxic lesions produced by the mitochondrial toxin malonate resemble those of focal cerebral ischemia. Intrastriatal injections of malonate induced cleavage of caspase-2 beginning at 6 h, and caspase-3-like activity as identified by DEVD biotin affinity-labeling within 12 h. DEVD affinity-labeling was prevented and lesion volume reduced in transgenic mice overexpressing BCL-2 in neuronal cells. Intrastriatal injection of the tripeptide, N-benzyloxycarbonyl-Val-Ala-Asp-fluoromethylketone (zVAD-fmk), a caspase inhibitor, at 3 h, 6 h, or 9 h after malonate injections reduced the lesion volume produced by malonate. A combination of pretreatment with the NMDA antagonist, dizocilpine (MK-801), and delayed treatment with zVAD-fmk provided synergistic protection compared with either treatment alone and extended the therapeutic window for caspase inhibition to 12 h. Treatment with cycloheximide and zVAD-fmk, but not with MK-801, blocked the malonate-induced cleavage of caspase-2. NMDA injections alone resulted in a weak caspase-2 cleavage. These results suggest that malonate toxicity induces neuronal death by more than one pathway. They strongly implicate early excitotoxicity and delayed caspase activation in neuronal loss after focal ischemic lesions and offer a new strategy for the treatment of stroke.

Glial tumor invasion: a role for the upregulation and cleavage of BEHAB/brevican.

Glial tumors, gliomas, are the most common primary intracranial tumors. Their distinct ability to invade the normal surrounding tissue makes them difficult to control and nearly impossible to completely remove surgically, and it accounts for the extraordinarily high lethality associated with gliomas. The ability of these transformed glial cells to invade the normal surrounding tissue is relatively unique in the adult CNS, which under most circumstances, is inhibitory to cell movement. The extracellular matrix (ECM) can modulate, in part, the permissiveness of a tissue to cell movement. Accordingly, the ability of gliomas to modify the ECM of the CNS may mediate the invasiveness of these cells. One ECM molecule that shows dramatic upregulation in gliomas is BEHAB (brain enriched hyaluronan binding)/brevican, a brain-specific chondroitin sulfate proteoglycan. BEHAB/brevican expression is also upregulated during periods of increased glial cell motility in development and following brain injury. Experimental evidence suggests that in glioma, in addition to upregulation of BEHAB/brevican, proteolytic processing of the full-length protein also may contribute to invasion. Here, the authors present a review of the literature on glial tumor invasion by modulation of the ECM and propose a two-step model for BEHAB/brevican's role in this process.

Improved therapeutic window for treatment of histotoxic hypoxia with a free radical spin trap.

The therapeutic time window for N-methyl-D-aspartate (NMDA) antagonists, non-NMDA antagonists, and glutamate release inhibitors in focal models of ischemia appears to be about 1-2 h. In contrast, a free radical spin trap was found to have an improved therapeutic window. We compared the therapeutic time windows of the NMDA antagonist dizolcilpine maleate (MK-801), the glutamate release inhibitor lamotrigine, and the free radical spin trap n-tert-butyl-alpha-(2-sulfophenyl)-nitrone (S-PBN) against striatal lesions produced by the mitochondrial toxin malonate, which produces histotoxic hypoxia. Lamotrigine exerted neuroprotective effects when administered at 1 h before malonate injections. MK-801 protected at 1 h before and 1 h after malonate injections, whereas S-PBN showed efficacy when administered up to 6 h after malonate injections. Striatal injections of malonate produced a rapid increase in lactate production and early changes in diffusion-weighted imaging as assessed by magnetic resonance imaging. Therefore, the time course to evolve a lesion in our model of histotoxic hypoxia is comparable with that of other models of focal ischemia. These findings provide direct evidence that a free radical spin trap has an improved therapeutic window compared to an NMDA antagonist and a glutamate release inhibitor. This could be a therapeutic advantage in the treatment of clinical stroke patients.

Coenzyme Q10 in the central nervous system and its potential usefulness in the treatment of neurodegenerative diseases.

Coenzyme Q10 is an essential cofactor of the electron transport chain and is an antioxidant. We examined the effects of oral feeding with coenzyme Q10 in young animals on brain concentrations. Feeding with coenzyme Q10 at a dose of 200 mg/kg for 1-2 months in young rats resulted in significant increases in liver concentrations, however, there was no significant increase in brain concentrations of either reduced- or total coenzyme Q10 levels. Nevertheless there was a reduction in malonate-induced increases in 2,5 dihydroxybenzoic acid to salicylate, consistent with an antioxidant effect. In other studies we found that oral administration of coenzyme Q10 significantly reduced increased concentrations of lactate in the occipital cortex of Huntington's disease patients. These findings suggest that coenzyme Q10 might be useful in treating neurodegenerative diseases.

Neurotensin depolarizes cholinergic and a subset of non-cholinergic septal/diagonal band neurons by stimulating neurotensin-1 receptors.

Identified cholinergic and a subtype of non-cholinergic, fast-firing neurons were recorded intracellularly in vitro from slices of guinea-pig brain. Recorded neurons were within the boundaries of the medial septum and vertical limb of the diagonal band of the forebrain. The effects of superfused neurotensin and neurotensin receptor antagonists were measured under single-electrode current clamp. Neurotensin consistently caused a dose-dependent, slow depolarization of cholinergic neurons that was accompanied by an increase in membrane resistance and a block of the long-duration (1-10 s) post-spike afterhyperpolarization when present. Neurotensin also blocked a shorter duration, slow afterhyperpolarization, but only in a minority of cholinergic neurons. When present, inhibition of the slow afterhyperpolarization changed the spike pattern from single spikes to short bursts. Inhibition of post-spike afterhyperpolarizations by neurotensin reversed more slowly than did other effects of neurotensin. Tetrodotoxin did not prevent the depolarizing effect of neurotensin. The non-selective neurotensin receptor antagonist, SR142948A, blocked the depolarizing effect of neurotensin but the low-affinity receptor antagonist, levocabastine, did not. A subgroup of noncholinergic, fast-firing neurons (23%) was also depolarized by neurotensin, an effect antagonized by SR142948A but not levocabastine. Neurotensin did not effect post-spike voltage transients or change the firing pattern of non-cholinergic neurons. These data suggest that neurotensin causes a slow depolarization and increased excitability of cholinergic and some noncholinergic neurons in an area of the brain that projects to the hippocampus. Neurotensin type 1 receptors appear to mediate these effects. Neurotensin may modulate hippocampal-dependent learning and memory processes through its effects on septohippocampal neurons.

Electrophysiological evidence for excitation of rat ventral tegmental area dopamine neurons by morphine.

A considerable body of evidence indicates that opiates have an important influence on midbrain dopaminergic neurons. However, little data exist concerning the effects of opiates on the activity of single dopaminergic neurons, particularly the dopaminergic neurons of the ventral tegmental area. Firing rates of mesencephalic dopaminergic neurons were recorded extracellularly, and the effects of morphine, administered systemically or applied locally onto dopaminergic cells, were tested in paralyzed, unanesthetized or chloral hydrate anesthetized rats. In general, dopaminergic neurons were excited by both systemically and locally applied morphine. When mesencephalic dopaminergic neurons were subdivided into substantia nigra zona compacta (A9) and ventral tegmental area (A10) neurons, A10 neurons were excited 2-3 times more than A9 neurons by systemic morphine. Systemic administration of the specific opiate antagonist, naloxone, in large part reversed the effects of morphine. Microiontophoretic or micropressure ejection of morphine caused an apparent depolarization-induced excitation of both A10 and A9 dopaminergic neurons. These results provide direct evidence that morphine increases impulse flow of A10 dopaminergic neurons, which are known to be involved in locomotor stimulant and positive reinforcement effects of opiates.

A comparison of extracellular and intracellular recordings from medial septum/diagonal band neurons in vitro.

Firing patterns, action potential characteristics and some active membrane properties of guinea-pig medial septum/diagonal band neurons were studied in an in vitro slice preparation. A comparison was made between several types of cells classified according to either extracellularly recorded (n = 130) or intracellularly recorded (n = 30) electrophysiological characteristics. Using multi-barrel extracellular electrodes, three principal cell types were distinguished: slow rhythmic firing cells (29%), fast rhythmic firing cells (65%) and burst-firing cells (6%). Most slow firing cells could also be distinguished from other cell types by their relatively longer action potential duration and a characteristic cadmium-sensitive "hump" in the repolarization phase of the action potential. These characteristics of slow firing cells matched well with the characteristics of cholinergic, slow afterhyperpolarization cells previously identified with intracellular recordings. The action potential shape, firing rate and firing pattern characteristics of about 60% of extracellularly recorded fast rhythmic firing cells matched those of previously identified non-cholinergic fast afterhyperpolarization cells. The remaining extracellularly recorded, rhythmic firing cells (about 10% of slow firing and 40% of fast firing cells) had a mixture of characteristics which precluded unequivocal classification as to cholinergic or non-cholinergic cell type. Using intracellular recording, the bee venom toxin, apamin, was shown to attenuate the characteristic post spike slow afterhyperpolarization of cholinergic cells and greatly enhanced their firing rate to depolarizing pulses. Apamin often attenuated a smaller and more transient afterhyperpolarization found in identified non-cholinergic cells, but firing rate was increased only slightly. Extracellular recordings from slow and fast rhythmic firing cells in the presence of apamin showed that excitability of slow firing cells was enhanced significantly more than fast firing cells. The apamin data support the hypothesis that extracellularly recorded slow firing cells are cholinergic. We conclude that extracellularly recorded medial septum/diagonal band cells characterized by broad action potentials, slow rhythmic firing under microiontophoresed glutamate and a signature "hump" in the falling phase of the action potential are cholinergic cells. Extracellularly recorded fast rhythmic firing cells with a narrow action potential and no "hump" in the action potential are likely to be non-cholinergic cells. This extracellular electrophysiological "fingerprint" for cholinergic medial septum/diagonal band cells in vitro may now be extended to studies in vivo where controversy remains as to the neurochemical identity of basal forebrain cells involved in control of hippocampal slow rhythmic activity.

Electrophysiological characteristics of non-bursting, glutamate decarboxylase messenger RNA-positive neurons of the medial septum/diagonal band nuclei of guinea-pig and rat.

Nuclei of the medial septum/diagonal band region of the mammalian forebrain contain neurons that give rise to the septohippocampal pathway, which has separate cholinergic and GABAergic components. This pathway is known to influence hippocampal-dependent memory and learning processes, but the precise role of each component is unclear. In this study, we tested the hypothesis that fast-firing, non-bursting medial septum/diagonal band neurons are GABAergic. We used brain slice preparations from young adult guinea-pigs and rats, or from weanling rats, to perform current-clamp recordings from medial septum/diagonal band neurons. Recorded neurons were injected with biocytin for subsequent visualization with fluorescent avidin, and then hybridized with a 35S-labeled riboprobe for glutamate decarboxylase-67 messenger RNA. As a positive control, guinea-pig cerebellar Purkinje cells were labeled and hybridized with the riboprobe. As expected, labeled Purkinje cells were glutamate decarboxylase-67 messenger RNA positive. Slow-firing, cholinergic (choline acetyltransferase-positive) guinea-pig medial septum/diagonal band neurons were glutamate decarboxylase-67 messenger RNA negative. Contrary to our hypothesis, of the guinea-pig neurons, only three of 11 fast-firing neurons were glutamate decarboxylase-67 positive. Of the rat medial septum/diagonal band neurons, three of four were positive for glutamate decarboxylase-67 messenger RNA. These data suggest that fast-firing, non-bursting neurons of the medial septum/diagonal band, as sampled by sharp-electrode intracellular recordings in brain slices, may be a heterogeneous group of neurons, some of which are GABAergic. Together with recent data demonstrating the presence of another GABAergic marker, parvalbumin, in fast-firing septal neurons, we conclude that GABAergic septohippocampal neurons include a population of fast-firing, non-bursting neurons. The influence of these neurons on the hippocampus is likely to occur on a shorter time-scale and over a wider range of firing frequencies as compared to slowly firing cholinergic septohippocampal neurons.

Association between protease-specific proteolytic cleavage of brevican and synaptic loss in the dentate gyrus of kainate-treated rats.

Proteolytic fragments generated by ADAMTS (a disintegrin and metalloprotease with thrombospondin motifs)-mediated cleavage of the aggregating chondroitin sulfate proteoglycan, brevican, have been identified, but not localized in the CNS. The purpose of this study, using kainate-induced CNS lesion, was to examine the spatial and quantitative relationship between ADAMTS1 and 4 mRNA expression and ADAMTS-mediated cleavage of brevican (as determined by the abundance of the neo-epitope QEAVESE at the C-terminal of the cleaved brevican G1 domain). In untreated rats, in situ hybridization and reverse transcriptase polymerase chain reaction indicated that ADAMTS4 expression was higher than ADAMTS1 and was localized to hippocampus, temporal lobe and other areas of cortex, striatum and hypothalamus. ADAMTS4 mRNA expression in these regions correlated with the presence of the QEAVESE neo-epitope, which was concentrated in perineuronal nets and in neuropil. In rats that seized after kainate, there was a dramatic elevation in ADAMTS1 and ADAMTS4 transcript that correlated and co-localized with a robust elevation in an extractable, 55-kDa fragment of brevican in temporal lobe and hippocampus. This fragment consisted, at least in part, of the ADAMTS-cleaved epitope G1-QEAVESE. The kainate-induced elevation in this ADAMTS-cleaved fragment was localized to amygdaloid and thalamic nuclei, hippocampus, caudate-putamen, cingulate cortex, and the outer molecular layer of the dentate gyrus where it was accompanied by a robust elevation in ADAMTS1 and 4 mRNA and a 28% decline in synaptic density 5 days after kainate.Thus, complexes of extracellular matrix proteins that exist in perineuronal nets and in the neuropil are cleaved by specific matrix-degrading proteases at early time points during excitotoxic neurodegeneration. The observed ADAMTS-induced cleavage of brevican in the dentate outer molecular layer is closely associated with diminished synaptic density, and may, therefore, contribute to synaptic loss and/or reorganization in this region.

Neuroprotective strategies for treatment of lesions produced by mitochondrial toxins: implications for neurodegenerative diseases.

Neuronal death in neurodegenerative diseases may involve energy impairment leading to secondary excitotoxicity, and free radical generation. Potential therapies for the treatment of neurodegenerative diseases therefore include glutamate release blockers, excitatory amino acid receptor antagonists, agents that improve mitochondrial function, and free radical scavengers. In the present study we examined whether these strategies either alone or in combination had neuroprotective effects against striatal lesions produced by mitochondrial toxins. The glutamate release blockers lamotrigine and BW1003C87 significantly attenuated lesions produced by intrastriatal administration of 1-methyl-4-phenylpyridinium. Lamotrigine significantly attenuated lesions produced by systemic administration of 3-nitropropionic acid. Memantine, an N-methyl-D-aspartate antagonist, protected against malonate induced striatal lesions. We previously found that coenzyme Q10 and nicotinamide, and the free radical spin trap n-tert-butyl-alpha-(2-sulfophenyl)-nitrone (S-PBN) dose-dependently protect against lesions produced by intrastriatal injection of malonate. In the present study we found that the combination of MK-801 (dizocipiline) with coenzyme Q10 exerted additive neuroprotective effects against malonate. Lamotrigine with coenzyme Q10 was more effective than coenzyme Q10 alone. The combination of nicotinamide with S-PBN was more effective than nicotinamide alone. These results provide further evidence that glutamate release inhibitors and N-acetyl-D-aspartate antagonists can protect against secondary excitotoxic lesions in vivo. Furthermore, they show that combinations of agents which act at sequential steps in the neurodegenerative process can produce additive neuroprotective effects. These findings suggest that combinations of therapies to improve mitochondrial function, to block excitotoxicity and to scavenge free radicals may be useful in treating neurodegenerative diseases.

Context-specific morphine withdrawal in rats: duration and effects of clonidine.

Rats previously injected with morphine in a particular environment (paired rats) emitted more withdrawal symptoms in that environment than did rats previously injected with morphine in another environment (unpaired rats) after both 1 day and 5 days of morphine abstinence. Thus, reexposure to an environment previously associated with morphine can elicit context-specific withdrawal even after several days of morphine abstinence. Clonidine (0.06 mg/kg) reduced most of the withdrawal symptoms seen 5 days after morphine abstinence in both the paired and unpaired rats. However, clonidine enhanced many of the withdrawal symptoms in both groups of rats during naltrexone-precipitated withdrawal 1 day after morphine abstinence.

NGF attenuates 3-nitrotyrosine formation in a 3-NP model of Huntington's disease.

Nerve growth factor (NGF)-secreting fibroblasts are able to protect against the Huntington-like striatal neurodegeneration induced by the mitochondrial toxin 3-nitropropionic acid (3-NP). In the present study, we investigated whether the neuroprotective effects of NGF are mediated through antioxidative mechanisms. Rats were grafted in the corpus callosum with NGF[+] or NGF[-] fibroblasts 7 days before administration of 3-NP. The generation of peroxynitrite was evaluated by measuring the striatal levels of 3-nitrotyrosine. NGF significantly decreased the 3-NP induced generation of 3-nitrotyrosine, presumably by decreasing peroxynitrite formation. These findings suggest that NGF might protect against neuronal death by inhibiting the production of nitric oxide or decreasing the levels of superoxide radicals, thereby decreasing the generation of oxidative agents such as peroxynitrite.

Increased 3-nitrotyrosine in brains of Apo E-deficient mice.

Apolipoprotein E (Apo-E) is linked to the pathogenesis of Alzheimer's disease. Apo-E deficient mice have increased lipid peroxidation in plasma. In the present study we examined two markers of oxidative stress in brains of Apo-E deficient mice. The ratios of 2,3 and 2,5 dihydroxybenzoic acid (DHBA)/salicylate, an index of hydroxyl radical generation, were unchanged except for an increase in 2.5-DHBA/salicylate in the cerebellum. 3-Nitroxyrosine is a marker for nitration of proteins produced by peroxynitrite. Concentrations of 3-nitrotyrosine were significantly increased in the cerebral cortex, hippocampus, brainstem and cerebellum of Apo-E deficient mice. These results suggest the Apo-E may modulate oxidative stress produced by peroxynitrite.

Coenzyme Q10 attenuates the 1-methyl-4-phenyl-1,2,3,tetrahydropyridine (MPTP) induced loss of striatal dopamine and dopaminergic axons in aged mice.

We investigated whether oral administration of coenzyme Q10 (CoQ10) could attenuate 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP) neurotoxicity in one-year-old mice. Four groups of one-year-old, male C57BL/6 mice received a either standard diet or a diet supplemented with CoQ10 (200 mg/kg/day) for five weeks. After four weeks, one group that had received the standard diet and one group that had received the CoQ10 supplemented diet were treated with MPTP. The four groups continued on their assigned diets for an additional week prior to sacrifice. Striatal dopamine concentrations were reduced in both groups treated with MPTP, but they were significantly higher (37%) in the group treated with CoQ10 and MPTP than in the group treated with MPTP alone. The density of tyrosine hydroxylase immunoreactive (TH-IR) fibers in the caudal striatum was reduced in both MPTP-treated groups, but the density of TH-IR fibers was significantly (62%) greater in the group treated with CoQ10 and MPTP than in the group treated with MPTP alone. Our results indicate that CoQ10 can attenuate the MPTP-induced loss of striatal dopamine and dopaminergic axons in aged mice and suggest that CoQ10 may be useful in the treatment of Parkinson's disease.